The present disclosure relates to semiconductor memories and, more particularly, to nonvolatile memory systems and operating methods of the same.
Semiconductor memory device are memory devices implemented using a semiconductor such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), and indium phosphide (InP). In broad terms, semiconductor memory devices are classified into volatile memory devices and nonvolatile memory devices.
In contrast to nonvolatile memory devices, volatile memory devices lose their stored data when their power supplies are interrupted. Nonvolatile memory devices retain their stored data even when their power supplies are interrupted. Volatile memory devices may include, for example, a static random access memory RAM (SRAM), a dynamic RAM (DRAM), a synchronous DRAM (SDRAM), or the like. Nonvolatile memory devices may include, for example, a read only memory (ROM), a programmable ROM (PROM), an electrically programmable ROM (EPROM), an electrically erasable and programmable ROM (EEPROM), a flash memory device, a phase change RAM (PRAM), a magnetic RAM (MRAM), a resistive RAM (RRAM), and a ferroelectric RAM (FRAM), or the like.
Flash memories have been used in a variety of applications due to low noise, low power consumption, and high-speed operation. A flash memory performs a read operation and a write operation in units of pages different from a data management unit of a host and has an “erase-after-write” characteristic, unlike a typical hard disk. Therefore, a separate management method is used.
In general, a storage device based on a flash memory manages data via a flash translation layer (FTL). The flash translation layer performs an operation to translate a logical address from a host into a physical address of the storage device. In particular, when data is erased by the host, a flash memory-based storage device processes data by updating a mapping table managed by the flash translation layer, and treating stored data as invalid data—instead of actually erasing the stored data. Consequently, since user data is retained in the storage device even when the user data is “erased” by the host, a user data security problem exists, because the data is not necessarily erased in the storage device.
Recently, focus has been shifting toward improved security among consumer and business devices. For example, some programs or applications encode user data to improve security and erase the user data after the lapse of predetermined time. However, as mentioned above, since actual data is retained in a flash memory-based storage device even when user data is thought to be erased, a user data security problem persists. Embodiments of the inventive concept disclosed herein address these and other problems.